6ATA-2 and Win2K...power supply?

I installed Win2k SP4 on my old comp.:

Chaintech 6ATA-2
Pentium III 800EB/256/133/1.65V SL3Y2 Socket 370
ASUS Radeon 7000 64MB
HDD Maxtor DiamondMax Plus 40GB
HDD Fujitsu 6GB
Aopen DVD 1648/AAP
ASUS CDR-W 4816-A

and I have some problem to boot Win2k.
After I switch on power, if I leave for a while my comp. on, for example
entering to BIOS setting, waiting for some seconds and exit without saving,
Win2K starts in a right way.
If I want to start Win2k immediatly I have an error:

*** STOP 0x00000067 (0x00000004, 0x0000007, 0x00000000, 0x00000000)
CONFIG_INIZIALIZATION_FAILED

I reset and reload and all works fine again.

My power supply has Max Output Power: 250Watt, is it too small?
Before I had Win98 on the same hardware and never I had problems.

Thanks
Giancarlo